N-cyanoethyl benzothiazole sulfenamides



United States Patent N-CYANOETHYL BENZQTHIAZOLE SULFENAMIDES' Dwight L. Schoene, Woodbridge, and Norman K. Sundholm, Naugatuck, Cnn., assignors to United States Rubber Company, New York, N. Y., a corporation of New Jersey No Drawing. Application July 27, 1954, Serial No. 446,175

Claims. (Cl; 260--306.6)

This invention relates to new compositions of matter valuable as accelerators for the vulcanization of rubber or other vu'lcanizable rubber like substances.

An object of the invention is to provide a new class of accelerators which have superior delayed action so that they can be used in rubber compounds reinforced with the very active (scorchy) furnace blacks. It is a further object to provide rubber compounds which can be processed at higher than the conventional temperatures before curing. Another object is to make available new compositions of matter.

The accelerators of the present invention comprise N- beta-cyanoethyl-Z-benzothiazolesulfenamides represented by the structure C-S-Cl ZRNHGHrCHzCN -r The amino nitrogen atom of the beta-aminopro'pionitrile must be attached to at least one hydrogen atom. Compounds of this type are prepared readily by the reaction of ammonia or a primary amine with acrylonitrile illustrated by:

whereR is H or hydrocarbon. Examples of beta-aminopropionitriles which can be used to prepare the compounds of this invention are beta-aminopropionitrile, betamethylaminopropionitrile, beta-isopropylaminopropionitrile, beta-cyclohexylaminopropionitrile, beta-benzylaminopropionitrile, beta-anilinopropionitrile, bis(beta-cyanoethyl) amine, and the like.

The 2-benzothiazolesulfenyl chloride used may be prepared by the chlorination of benzothiazolyl disulfide in an organic solvent as shown by U. S. patent to W. E. Messer No. 2,257,974.

CHzCHnON 2. Examples of N-beta-cyanoethyl-Z-benzothiazolesulfenamides and their preparation and properties are as follows:

Example 1.--N-is0propyl-N-beta-cyanoethyl-Z-benzothiazolesulfenamide Chlorine (14.5 grams) was passed in above a stirred suspension of 68 grams of technical benzothiazolyl disulfide in 500 ml. of anhydrous ethylene chloride at 25-30 C. during 30 minutes. The resulting dark red solution of 2-benzothiazolesulfenyl' chloride was added dropwise to a stirred solution of 89.6 grams of beta-isopropylaminopro- PlOIlilITilB'lIl 200 ml. of anhydrous ethylene chloride during two and one-half hours. The reaction mixture was kept at 19-21 C. by the use of an ice-water bath. After stirring for 30 minutes sufiicient water was added with stirring to dissolve the beta-isopropylaminopropionitrile hydrochloride formed during the reaction. The organic layer was separated from the water layer and the ethylene chloride removed. The residual product weighed 106 grams (95% of theory) and melted at -83 C. The material was purified by recrystallization from 75% eth anol and then from ligroin (B. P. 60-90 C.) using decolorizing carbon to give colorless crystals melting at 84.5 C.

Analysis. Calculated for C13H15N3S2: Found: N, 14.82.

The remaining examples were prepared using the above procedure.

Example 2.N-methyl-N-beta-cyanoethyl-Z-benzothiazolesulfenamide This compound was prepared from 2-benzothiazolesulfenyl chloride and beta-methylaminopropionitrile. It was obtained as an oil.

Analysis.-Calculated for Cull-111N382: N, 16.87; S, 25.70. Found: N, 16.09; S, 25.45.

Example 3.N-cyclohexyLN-beta-cyanoethyl-Z-benzothiazolesulfenamide This compound was prepared from Z-benzothiazolesulfenyl chloride and beta-cyclohexylaminopropionitrile. It was purified by recrystallization from ligroin (B. P. 60 C.) and then from acetone to give colorless crystals melting at 77-78.5 C.

Analysis-Calculated for C1sH19NaS2: N, 13.25; S, 20.19. Found: N, 12.75; S, 20.21.

Example 4.-PN-benzyl-N-beta-cyan0ethyl-2-benzothiazolesulfenamide This compound was prepared from 2-benzothiazolesulfenyl chloride and beta-benzylaminopropionitrile. It was purified by recrystallization from ethanol using decolorizing carbon to give colorless crystals melting at 69.5-70.5 C

Analysis.--Calculated for cmHisNs-Sz: N, 12.92. Found: N, 12.60.

Example 5.-N-phenyl-N-beta-cyanoethyl-Z-benzothiazolesulfenamide Example 6.N,Nbis(beta-cyanoethyl)-2-benz0thiazolesulfenamide This compound was prepared from 2-benzothiazolesul fenyl chloride and bis(beta-cyanoethyl)amine. It was purified by recrystallization from ethanol using decolorizing carbon to give colorless crystals melting at C.

N Analysis-Calculated for C13H12N4S2:N, 19.44. Found:

To demonstrate the utility of these new compositions of matter :as accelerators for the vulcanization of rubber, examples were incorporated into the following formula:

Parts by weight Smoked sheet 100 Super abrasion furnace black 45 Zinc oxide-" Zinc salts of cocoanut oil acids 3.5 Pine tar 3.5 Antioxidant 2.0 Sulfur 2.25 Accelerator 0.5

Stocks were compounded containing as the accelerator 'the following:

Stock Accelerator Benzothiazolyl disulfide. N-lliethyl-N-beta-cyanoethyl-2-benzothiazole-snlfenamide. N I sopropyl N beta-cyanoethyl-2-benzotbiazole-sulfenanude. N-Qgclohexyl-N-beta cyanoethyl-zbenzothiazole-snlfenam N -Benzyl-N -beta-cyanoethyl-zbenzotbiazole-sulfenamido. N .N-bis(beta-Cyanoethyl)-2-benzothiazolesulfenamide.

The stocks were cured by heating in a press at 292 F. for various periods of time. The physical properties of the respective stocks at the respective curing times are given in the following table:

The data obtained after curing for 60 minutes show these new compositions of matter to be. excellent accelerators. compared to benzothiazolyl disulfide in stock A show them to have superior delayed action.

in order to demonstrate further the delayed action of these new accelerators, the scorch times of these stocks were measured on the Mooney viscometer at 250 F. and 280 F.

Scorch time at- Stock Min. Min.

These accelerators may be used to accelerate the vulcanization of any of the natural or synthetic rubbers which ordinarly lend themselves to cure with sulfur or other curing agent Whose curing action is susceptible to acceler- The low degrees of cure after 15 minutes when ation, and which include the rubber-like homopolymers of butadiene-1,3 and substituted butadienes, and rubbery copolymers of the same with aryl olefins such as styrene, with acrylic compounds such as methyl acrylate, methyl methacrylate and acrylonitrile, as well as with isobutylene, methyl vinyl ether, mono-vinylpyridines, vinylidene chloride, etc. Better known synthetic rubbers are neoprene, butadiene-styrene (GR-S), and butadiene-acrylonitrile (GR-A). Accordingly, the expression a rubber refers to such natural and artificial rubbers.

The new accelerators may .be added to the rubber by mill incorporation, by impregnation, by addition to latex, or other dispersions thereof, and the stocks may be subjected either to mold cures, air cures, submarine cures, steam cures, etc. Further, various compounding ingredients, such as fillers, pigments, softeners, antioxidants, etc., may be added.

The accelerators may be cured with or without the aid of conventional accelerator activators, e. g., diphenylguanidine, or in conjunction with other conventional accelerators (e. g., mercaptobenzothiazole or benzothiazolyl disulfide).

The proportions of the accelerator may be the same as, and need not exceed the proportions in which other conventional rubber accelerators are used, and are usually from 0.2 to 3 percent, based on the rubber component.

Having thus described our invention, what we claim and desire to protect by Letters Patent is:

1. Compounds represented by the formula sulfenamide.

4. Compounds represented by the formula where R represents an aliphatic hydrocarbon radical having from 1 to 12 carbon atoms.

5. Compounds represented by the formula where R represents an alkyl hydrocarbon radical having from 1 to 12 carbon atoms.

CHa-CHa-CN References Cited in the file of this patent UNITED STATES PATENTS 2,367,827 Smith Jan. 23, 1945 2,407,138 Clifford et a1. Sept. 3, 1946 2,560,045 Smith July 10, 1951 2,581,936 Carr Jan. 8, 1952 2,585,155 Mingasson Feb. 12, 1952 2,695,904 Cooper July 31, 1952 

1. COMPOUNDS REPRESENTED BY THE FORMULA 